Conducting a Cat 3B No Decision Height Autoland and passed RVRs prior to the outer marker of 200m/150m/150m. I have Cat 3A reversion.
The Tower then passes 125m/125m/125m after the outer marker and shortly afterwards the ASA then downgrades to LAND2. Do I have to go around as I no longer have Cat 3A minima or can I continue to my Cat 3A decision height ?
Two seperate issues here:
The first is the controlling RVR requirement. Provided that is equal to, or better than the specified minima for the plannned approach, at the outer marker (or equivalent position) the approach may be be continued to the applicable Decision height, even if the RVR subsequently reduces below the previous governing minima.
However the second part of your question concerns a technical degradation in the autopilot system. Once past the outer marker (or equivalent position) a change from "land 3" to "land 2" (above 200 ft) requires that the Cat 2 minimum height becomes the governing factor. The visibility (although not the visual requirements) is irrelevant.
To answer your question. The change in autoland status, once past the OM (EQV position) has no mandatory effect on the continuance of the approach, however the change in autoland technical status (above 200ft) does require the application of the new decision height requirement. In this situation you cannot continue to your Cat 3A decision height (if above 200ft) but you do not need to Go around, as you can continue to the now governing Cat 2 decision height.
These rules are slightly different in the USA, whereby the approach (post OM/FAF) can only be continued to the Alert height if the controlling RVR's drop below minima.